Methods for the prevention and control of hospital-acquired urinary tract infections associated with indwelling urethral catheters will be evaluated by prospectively controlled studies. Control methods to be evaluated include: (1) improved aseptic care of closed urinary drainage systems by a catheter-care team; (2) continuous bladder irrigation with antibacterial solutions; and (3) prompt short-term use of systemic antimicrobial agents as soon as bacterial colonization is recognized in a program of intensive bacteriologic surveillance of drainage systems.